As a high school junior my only EC is debate. I was state qualified as a sophomore. I am TOC qualified, NSDA AAA, NSAD national championship qualifier, president Coolidge debate cup qualified, state qualified as a junior. Academically I am in top 1% of the class and SAT score of 1570. I want to do Engineering. Without any stem related EC what are my chances in top engineering school.
Debate is an excellent EC. AO’s also know it’s a huge tome sink so top contenders often have few other EC’s.
Another bonus: You can often use topics from debate in essays in the classroom or even college essays.
It’s not uncommon for debaters to have top SAT scores in English as the required reading and synthesis of various ideas is a tranferabke skill.
Have you thought about sharing some of your written work via the student paper/magazine/local paper? That could expand your ecs with little effort.
Perhaps unjustified, engineers are often perceived to be lacking in their abilities to communicate with others outside of their fields; your demonstrated communication skills should be valuable in helping you to stand out among the applicants.